Combined rapid traverse and slow traverse hydraulic system



H. F. VICKERS Dec; 4, 1934.

COMBINED RAPID TRAVERSE AND SLOW TRAVERSE HYDRAULIC SYSTEM 8 R wk l m Aw T F ,8 M M fi m w 0 V: B 0 q a J AI 3 l 9n FAIU r. w w

Patented Dec. 4, 1934 UNITED STATES COMBINED RAPID TRAVERSE AND SLOW TRAVERSE HYDRAULIC SYSTEM Harry F. Vickers, Detroit, Mich.

Application October 19,

13 Claims.

This invention relates to a combined rapid traverse and slow traverse hydraulic system, and has to do particularly with a hydraulic system requiring a rapid traverse at low pressure and a slow traverse work stroke at high pressure.

The object of the present invention is to provide a plurality of positive displacement pumps, driven at the same speed, in combination with a circuit and automatically controlled valve which furnish a variable flow of fiuid at a minimum loss of power. More specifically, the invention contemplates the combination of two positive displacement pumps with suitable valves and conduits for causing both pumps to deliver into a common conduit up to a predetermined pressure whereupon the flow from one pump is diverted back to the source of supply at substantially no pressure while the other pump continues to deliver into the power conduit at a higher pressure; the direct result being a considerable saving of power on any machine tool or press circuit wherein a rapid traverse to or from a given point at a comparatively low pressure and a much slower traverse at a higher pressure is desired.

In the drawing:

Fig. 1 illustrates a double pump unit and a somewhat diagrammatic circuit for controlling the flow of fluid.

Fig. 2 is a view somewhat similar to Fig. 1 but showing in addition a diagrammatic hook-up of the power cylinder and a speed control valve for controlling the operation of the piston.

In the preferred embodiment of my invention I have shown a relatively small pump 1 and a relatively large pump 2 connected in parallel and operated on a single shaft from a common motor 3. The pumps 1 and 2 are connected by suitable conduits 4 and 5 to a supply tank 6 and in normal operation are adapted to feed the fluid under pressure through conduits 7 and 8 which flow intoa common power line 9.

A low pressure by-pass valve 10 is connected into the conduit 8 and consists of a main passageway, a branch conduit 12, leading to the supply tank 6, an operating piston 13, a spring 14 of predetermined value, and a conduit 15 leading from the pressure conduit 7 into the front face of the piston 13. With this arrangement it will be obvious that when the pressure in the conduit 15 overcomes the pressure of the spring 14, the liquid in the conduit 8 will be conducted back to the supply tank 6 so that there will be substantially no load because of the pump member 2.

A check valve 16 is inserted at a point to pre vent the working or high pressure pump 1 from 1931, Serial No. 569,612

pumping into the open line of the idling pump. A high pressure balanced relief valve 1'7 is connected in between the main power conduit and the main return conduit 18. As shown, this relief valve 17 is of the type shown and described in my copending application Serial No. 552,692, filed July 23, 1931, but it will be understood that any suitable relief valve may be used at this point. It will be obvious that this relief valve will control the working pressure during the slow traverse high pressure stroke of the unit. In this type of valve the balancing is obtained by a plunger 19 and the relieving pressure is determined by an adjustable control valve 20.

In operation, it may be assumed that the pump 1 has a pressure of 200 pounds at h. p., the combined pumps 1 and 2 operating on a rapid traverse at say 20 gallons per minute at 3% h. p. If the spring 14 is set to work at 200 pounds the by-pass valve 10 will open at the beginning of the work or slow traverse stroke, where high pressure is required, and the No. 2 pump will be cut out and will return all liquid pumped therefrom back to the source of supply at substantially no load. The No. 1 pump will now be operating alone and at '700 pounds pressure this pump would give approximatelyGM; gallons per minute using3 h. p.

However, if a single pump is used of 20 gallon capacity, and then using 700 pounds pressure during the work stroke, most of the volume will be going over the relief valve and the pump would still be using approximately 11 h. p. With the arrangement of two pumps working during the rapid traverse stroke only 3%, h. p. is used and during the slow traverse stroke only 3 h. p. is used. The above figures are given as only one example, but it will be readily seen that a large volume pump working during the rapid traverse stroke and cutting out during the high pressure slow traverse stroke will save considerable power and heat on the particular types of installations with which it may be used.

In the modification illustrated in Fig. 2, I have substituted a simple relief valve 21 in place ,of the balanced relief valve 17. I have also shown the system as being connected up with a power cylinder 22 and a conventional valve 23 for controlling the operation of such power cylinder. To the return line 24 of this system I have connected in a speed control valve 25 which will control the speed of movement of the piston in the cylinder 22.

This speed control valve, as shown, is of the type illustrated and described in my copending application Serial No. 543,908, filed June 12, 1931,

' ential across a given sized orifice to positively control the speed of the piston. independently of the load. A'valve 28 is preferably provided for cutting the speed control valve 25 into the sys- 'tem at any 7 by-pass valve 28 may be open while both pumps during the rapid traverse low pressure stroke and being cut in when the piston 13 is actuated to cut out pump No. 2.

Another possible method of operation with the combination shown in Fig. 2 would be the positioning of the regulableorifice control valve 26 which may be set at a certain point to control the speed of the piston and the cylinder 22 during the rapid traverse low pressure stroke and at another point to control the speed of the same piston during the slow traverse high pressure stroke. It will thus be seen that various combiarranged to'be normally nations and methods of operation are possible with the combination shown in Fig. 2 whether either or both pumps are used during either the forward or return stroke of the operating tool, or whether the speed control valve is by-passed or adjusted during part or all of the stroke of the piston in either or both directions. Valve 28 is the valve which may be operated at will to cut the rapid traverse step in and out.

What I claim is:

1. A liquid circulating system comprising in combination a source of liquid supply, a liquid operated motor, a plurality of continuously operating continuously circulating pumps, conduits leading from said pumps for conducting liquid under pressure to said motor, a by-pass valve in one of said conduits adapted to conduct liquid from one of said pumps back to the source of supply, a connection between the discharge side of another pump and said by-pass valve for actuating said by-pass valve and relieving said first named pump only upon the building up of a predetermined pressure in the discharge line of said second named pump, and means for preventing the fluid pressure in the discharge line of said second pump from entering the first named pump or by-pass valve at any time.

2. A system for transmitting power by liquid, comprising a member to be operated at .a relatively high speed and low pressure and also a relatively low speed and high pressure, a source of liquid supply, a relief valve for controlling the pressure during the low speed operation, a plurality of continuously operating and circulating pumps of different volumetric capacity for transmitting the liquid under pressure from said source of supply to the member to be actuated, said pumps combining to supply a relatively large volume of liquid at a relatively low pressure, means in the discharge side of one of said pumps and directly responsive to an increase in said pressure for cutting said pump out of the system and supplying liquid at a high pressure from the other pump, and a one way check valve between the discharge sides of two of said pumps and between said means and liquid operated memher.

3. In a liquid circulating system, the combination of a liquid operated motor of the type having a rapid traverse low pressure stroke and a slow traverse high pressure stroke, a source of liquid supply, a relief valve for controlling the pressure during the slow traverse stroke, a plurality of point desired. In other words, the

1 and 2 are operating-check valve positioned and embodies a regulable orifice outlet valve 26 positive displacement pumps moimted upon the same operating shaft, conduits for conducting, the

liquid under pressure from the plurality of pumps to a single line leading into the motor,means posie tioned in the conduit leading from one of said pumps and directly responsive to a. predetermined I increase in pressure between said pumps and mo-' tor for by passing-the liquid passing through said pump back to the source of supply, and a one way between said means and said single line,

4. In a liquid circulating system of the type having a liquid operated motor having a rapid traverse low pressure stroke and a slow traverse high pressure stroke, the combination of a continuously operating relatively large volume pump and a continuously operating relatively small volume pump, conduits for conducting the liquid under pressure to the motor from both of said pumps during the rapid traverse stroke, means directly responsive to an increase in pressure between the pumps and, motor for automatically returning the liquid passing through the relatively large volume pump back to the source of supply during the slow traverse high pressure stroke of the motor, and a one way check valve positioned between said means and said small volume pump conduit and motor.

5. In a liquid circulating system of the type having a liquid operated motor having a rapid traverse low pressure stroke and a slow traverse high pressure stroke, the combination of a relatively large volume and relatively small volume pump mounted on the same operating shaft, a relief valve for determining the operative pressure during the slow traverse stroke, conduits for conducting the liquid under pressure to the motor from both of said pumps during the rapid traverse stroke, and means responsive to an increase in pressure for automatically returning the liquid passing through the relatively large volume pump back to the source of supply during the slow traverse high pressure stroke of the motor, and a one way check valve positioned between said ioo means and said small volume pump conduit and 20 motor.

6. In a liquid circulating system of the type having a motor designed to be operated at different pressures, the combination of two pumps mounted upon the same operating shaft, a source of supply continuously conducted to said pumps, conduits leading from said pumps to the motor to be operated, a by-pass valve mounted in one conduit and adapted upon operation to conduct the liquid in said conduit back to the source of supply, a connection between the other conduit and said by-pass valve for operating the by-pass valve whereby the one pump is by-passed or returned back to the source of supply depending upon the pressure existing in the conduit leading from the other pump, and a one way check valve between said two conduits.

'7. A system for transmitting power by liquid, comprising a liquid operated motor of the rapid traverse low pressure and slow traverse high pressure type, a source of liquid supply, a plurality of positive displacement pumps of different volumetric capacity connected in between said source of supply and the motor, a by-pass valve connected into the conduit leading from one of said pumps, means for opening said by-pass valve whenever the pressure in the main line leading to the motor exceeds a predetermined point, and a one way check valve between said by-pass valve and main line to the motor.

8. A system for transmitting power by liquid, comprising a liquid operated motor of the rapid traverse low pressure and slow traverse high pressure type, a source of liquid supply, a plu- 'rality of positive displacement pumps of different volumetric capacity connected in between said source of supply and the motor, a relief valve for determining the operative pressure during the slow traverse stroke, a by-pass valve connested into the conduit leading from the pump of largest volumetric capacity, means for opening said by-pass valve whenever the pressure in the main line leading to the motor exceeds a predetermined point, and a one way check valve between said by-pass valve and main line to the motor.

9. A two-volume pump circuit comprising in combination a continuous source ofliquid supply, two positive displacement pumps having different volumetric capacities, means for driving said pumps at a constant speed, conduits for transmitting the liquid under pressure from the pumps to a common operating conduit, the combined liquid in both pumps being transmitted through said common conduit up to a predetermined pressure, means directly responsive to said predetermined pressure to divert liquid from one pump back to the source of supply, and a one way check valve between said means and said common conduit.

10. A system for transmitting power by liquid comprising a plurality of positive displacement pumps of varying volumetric capacities, operated at the same speed, a motor operated by the liquid under pressure from said pumps, means for bypassing one of said pumps out of the-system in accordance with the pressure existing in the system, a check valve positioned between said means and the motor for keeping the fluid pressure existing in said system out of said one pump at any time, and means for controlling the speed of said liquid operated motor.

11. A liquid circulating system comprising in combination a source of liquid supply, a liquid operated motor of the rapid transverse low pressure and slow traverse high pressure type, a plurality of positive displacement pumps for delivering liquid under pressure to the motor, a relief valve for determining the operative pressure during the slow traverse stroke, means operable at a predetermined pressure set up between the pumps and motor for removing the load upon and returning the liquid from one of said pumps back to the source of supply, and a check valve, 0perable upon cutting said one pump out of the system, for keeping the pressure existing in the rest of the system out or said out out pump at any time.

12. In a liquid circulating system, the combination of a liquid operated motor of the type having a rapid traverse low pressure stroke and a slow traverse high pressure stroke, a source 01' liquid supply, a plurality of pumps mounted upon the same operating shaft, a relief valve for determining the operative pressure during the slow traverse stroke, conduits for conducting the liquid under pressure from the plurality of pumps to a single line leading into the motor, means positioned in the conduit leading from one of said pumps for by-passing said pump back to the source of supply when the liquid in the system reaches a predetermined pressure, and means positioned between the by-pass pump conduit and the other conduit or conduits for keeping the fluid pressure existing in the circulating system from entering the by-pass pump conduit at any time.

13. A system for transmitting power by liquid, comprising a work member to be operated at a relatively high speed and low pressure and also at a relatively low speed and high pressure, a source of liquid supply, a continuously operating low pressure pump and a continuously operating high pressure pump for transmitting liquid under pressure from the source of supply to the work member, a conduit leading from the high pressure pump to the work, an unloading valve, a one way check valve, a conduit leading from the low pressure pump through the unloading valve and the one way check valve and joining the first conduit, said two conduits and said pumps combining to supply a relatively large volume of liquid at a relatively low pressure, and a branch conduit connecting the conduit from the high pressure pump to the unloading valve for actuating the same upon development of a predetermined pressure.

HARRY F. VICKERS: 

